1. Purpose Visual subitising is the ability to quickly and intuitively enumerate small numbers of items, is hypothesized to be mediated by parallel processing. To examine any age-related variations in visual subitising performance. To understand how optical and neural changes with age 1 affect visual performance Methods Visual Stimulus Task: To enumerate the number of dots as quickly & accurately as they could Response latency: the time it took to say the number into a microphone On each trial, a number (1-10) of black dots was presented on the monitor screen for 200 ms. Dot diameter: 3 arcmin Randomly positioned in a 10 x 10 square (1 ◦ x 1 ◦ ) Minimum dot distance ≥ 9’ (edge-to-edge) Threshold: Midway between the upper & lower asymptotes of a Weibull psychometric function. 2 400 trials Viewing was binocular Subjects Normal macula, no lens & vitreous opacities … Visual acuity: 20/20 or better 7.170.61251760-90 3.555.31071751-60 3.344.6671341-50 2.834.27101731-40 2.622.71091921-30 SD (yrs) Mean age (yrs) Gender (F) Gender (M) Sample size Age group (yrs) Decreasing Visual Subitising Performance with Age Maya Kumar 1, Roger Li 1,2, Dennis Levi 1,2, Sandy Chat 1, & Manfred MacKeben 3 1 School of Optometry & 2 Helen Wills Neuroscience Institute, University of California-Berkeley, Berkeley, California, USA 3 The Smith-Kettlewell Eye Research Institute, San Francisco, California, USA Poster #890 Results Aging and Subitising Optical or Neural? Summary & Conclusions Older people have problems processing multiple objects at a time. Subitising, the quick assessment of small numbers of stimulus elements, is achieved through parallel processing. Such mechanisms are important where ever speed counts, e.g. in mobility and obstacle avoidance.. Visual subitising performance deteriorates with advancing age. Mean subitising thresholds: Systematically decreased from 7.1 (21-30) to 4.8 dots (61-90) across the 5 age groups. Roughly, 50% of the loss in threshold occurred by the age of 62. The response latency (61-90) was prolonged an average of ~ 30% (the latency curve shifted upward for 1 - 7 dots). For all age groups, the mean number of dots reported was very close to the number of dots displayed on the screen. The loss in subitising performance cannot be explained by the optical changes. Subitising threshold (21-40-yr-old) was minimally affected by reduced retinal illumination (0.2 log unit) and optical blurring (with ‘plus’ lens ~20/20). After training, the performance (67-yr-old) was still worse when compared with 21-30 group With longer stimulus durations, counting performance (67-86-yr-old) could be improved to reach young adult level. Acknowledgements The authors thank Jenny Sung for her help with collecting data. Research grants : NIH NEI R01EY01728 (DL) & The Smith-Kettlewell Eye Research Institute (MM) References 1.Li RW, Edwards MH, Brown B. Vis. Res. 2000; 40: 3775-3781. 2.Sharma V, Levi DM, Klein SA. Nat. Neurosci. 2000; 3: 496-501. Reduced Ret. Illumination Optical blurring to 20/20 Slow Learning Stimulus Duration F (4,78) =8.3 P < 0.0001 Duration (ms) 200 100 Target Mask SKERI T H E S M I T H – K E T T L E W E L L